xref: /openbmc/linux/arch/arm64/include/asm/uaccess.h (revision 68198dca)
1 /*
2  * Based on arch/arm/include/asm/uaccess.h
3  *
4  * Copyright (C) 2012 ARM Ltd.
5  *
6  * This program is free software; you can redistribute it and/or modify
7  * it under the terms of the GNU General Public License version 2 as
8  * published by the Free Software Foundation.
9  *
10  * This program is distributed in the hope that it will be useful,
11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13  * GNU General Public License for more details.
14  *
15  * You should have received a copy of the GNU General Public License
16  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
17  */
18 #ifndef __ASM_UACCESS_H
19 #define __ASM_UACCESS_H
20 
21 #include <asm/alternative.h>
22 #include <asm/kernel-pgtable.h>
23 #include <asm/sysreg.h>
24 
25 /*
26  * User space memory access functions
27  */
28 #include <linux/bitops.h>
29 #include <linux/kasan-checks.h>
30 #include <linux/string.h>
31 
32 #include <asm/cpufeature.h>
33 #include <asm/ptrace.h>
34 #include <asm/memory.h>
35 #include <asm/compiler.h>
36 #include <asm/extable.h>
37 
38 #define KERNEL_DS	(-1UL)
39 #define get_ds()	(KERNEL_DS)
40 
41 #define USER_DS		TASK_SIZE_64
42 #define get_fs()	(current_thread_info()->addr_limit)
43 
44 static inline void set_fs(mm_segment_t fs)
45 {
46 	current_thread_info()->addr_limit = fs;
47 
48 	/* On user-mode return, check fs is correct */
49 	set_thread_flag(TIF_FSCHECK);
50 
51 	/*
52 	 * Enable/disable UAO so that copy_to_user() etc can access
53 	 * kernel memory with the unprivileged instructions.
54 	 */
55 	if (IS_ENABLED(CONFIG_ARM64_UAO) && fs == KERNEL_DS)
56 		asm(ALTERNATIVE("nop", SET_PSTATE_UAO(1), ARM64_HAS_UAO));
57 	else
58 		asm(ALTERNATIVE("nop", SET_PSTATE_UAO(0), ARM64_HAS_UAO,
59 				CONFIG_ARM64_UAO));
60 }
61 
62 #define segment_eq(a, b)	((a) == (b))
63 
64 /*
65  * Test whether a block of memory is a valid user space address.
66  * Returns 1 if the range is valid, 0 otherwise.
67  *
68  * This is equivalent to the following test:
69  * (u65)addr + (u65)size <= current->addr_limit
70  *
71  * This needs 65-bit arithmetic.
72  */
73 #define __range_ok(addr, size)						\
74 ({									\
75 	unsigned long __addr = (unsigned long)(addr);			\
76 	unsigned long flag, roksum;					\
77 	__chk_user_ptr(addr);						\
78 	asm("adds %1, %1, %3; ccmp %1, %4, #2, cc; cset %0, ls"		\
79 		: "=&r" (flag), "=&r" (roksum)				\
80 		: "1" (__addr), "Ir" (size),				\
81 		  "r" (current_thread_info()->addr_limit)		\
82 		: "cc");						\
83 	flag;								\
84 })
85 
86 /*
87  * When dealing with data aborts, watchpoints, or instruction traps we may end
88  * up with a tagged userland pointer. Clear the tag to get a sane pointer to
89  * pass on to access_ok(), for instance.
90  */
91 #define untagged_addr(addr)		sign_extend64(addr, 55)
92 
93 #define access_ok(type, addr, size)	__range_ok(addr, size)
94 #define user_addr_max			get_fs
95 
96 #define _ASM_EXTABLE(from, to)						\
97 	"	.pushsection	__ex_table, \"a\"\n"			\
98 	"	.align		3\n"					\
99 	"	.long		(" #from " - .), (" #to " - .)\n"	\
100 	"	.popsection\n"
101 
102 /*
103  * User access enabling/disabling.
104  */
105 #ifdef CONFIG_ARM64_SW_TTBR0_PAN
106 static inline void __uaccess_ttbr0_disable(void)
107 {
108 	unsigned long ttbr;
109 
110 	/* reserved_ttbr0 placed at the end of swapper_pg_dir */
111 	ttbr = read_sysreg(ttbr1_el1) + SWAPPER_DIR_SIZE;
112 	write_sysreg(ttbr, ttbr0_el1);
113 	isb();
114 }
115 
116 static inline void __uaccess_ttbr0_enable(void)
117 {
118 	unsigned long flags;
119 
120 	/*
121 	 * Disable interrupts to avoid preemption between reading the 'ttbr0'
122 	 * variable and the MSR. A context switch could trigger an ASID
123 	 * roll-over and an update of 'ttbr0'.
124 	 */
125 	local_irq_save(flags);
126 	write_sysreg(current_thread_info()->ttbr0, ttbr0_el1);
127 	isb();
128 	local_irq_restore(flags);
129 }
130 
131 static inline bool uaccess_ttbr0_disable(void)
132 {
133 	if (!system_uses_ttbr0_pan())
134 		return false;
135 	__uaccess_ttbr0_disable();
136 	return true;
137 }
138 
139 static inline bool uaccess_ttbr0_enable(void)
140 {
141 	if (!system_uses_ttbr0_pan())
142 		return false;
143 	__uaccess_ttbr0_enable();
144 	return true;
145 }
146 #else
147 static inline bool uaccess_ttbr0_disable(void)
148 {
149 	return false;
150 }
151 
152 static inline bool uaccess_ttbr0_enable(void)
153 {
154 	return false;
155 }
156 #endif
157 
158 #define __uaccess_disable(alt)						\
159 do {									\
160 	if (!uaccess_ttbr0_disable())					\
161 		asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), alt,		\
162 				CONFIG_ARM64_PAN));			\
163 } while (0)
164 
165 #define __uaccess_enable(alt)						\
166 do {									\
167 	if (!uaccess_ttbr0_enable())					\
168 		asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), alt,		\
169 				CONFIG_ARM64_PAN));			\
170 } while (0)
171 
172 static inline void uaccess_disable(void)
173 {
174 	__uaccess_disable(ARM64_HAS_PAN);
175 }
176 
177 static inline void uaccess_enable(void)
178 {
179 	__uaccess_enable(ARM64_HAS_PAN);
180 }
181 
182 /*
183  * These functions are no-ops when UAO is present.
184  */
185 static inline void uaccess_disable_not_uao(void)
186 {
187 	__uaccess_disable(ARM64_ALT_PAN_NOT_UAO);
188 }
189 
190 static inline void uaccess_enable_not_uao(void)
191 {
192 	__uaccess_enable(ARM64_ALT_PAN_NOT_UAO);
193 }
194 
195 /*
196  * The "__xxx" versions of the user access functions do not verify the address
197  * space - it must have been done previously with a separate "access_ok()"
198  * call.
199  *
200  * The "__xxx_error" versions set the third argument to -EFAULT if an error
201  * occurs, and leave it unchanged on success.
202  */
203 #define __get_user_asm(instr, alt_instr, reg, x, addr, err, feature)	\
204 	asm volatile(							\
205 	"1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",			\
206 			alt_instr " " reg "1, [%2]\n", feature)		\
207 	"2:\n"								\
208 	"	.section .fixup, \"ax\"\n"				\
209 	"	.align	2\n"						\
210 	"3:	mov	%w0, %3\n"					\
211 	"	mov	%1, #0\n"					\
212 	"	b	2b\n"						\
213 	"	.previous\n"						\
214 	_ASM_EXTABLE(1b, 3b)						\
215 	: "+r" (err), "=&r" (x)						\
216 	: "r" (addr), "i" (-EFAULT))
217 
218 #define __get_user_err(x, ptr, err)					\
219 do {									\
220 	unsigned long __gu_val;						\
221 	__chk_user_ptr(ptr);						\
222 	uaccess_enable_not_uao();					\
223 	switch (sizeof(*(ptr))) {					\
224 	case 1:								\
225 		__get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr),  \
226 			       (err), ARM64_HAS_UAO);			\
227 		break;							\
228 	case 2:								\
229 		__get_user_asm("ldrh", "ldtrh", "%w", __gu_val, (ptr),  \
230 			       (err), ARM64_HAS_UAO);			\
231 		break;							\
232 	case 4:								\
233 		__get_user_asm("ldr", "ldtr", "%w", __gu_val, (ptr),	\
234 			       (err), ARM64_HAS_UAO);			\
235 		break;							\
236 	case 8:								\
237 		__get_user_asm("ldr", "ldtr", "%x",  __gu_val, (ptr),	\
238 			       (err), ARM64_HAS_UAO);			\
239 		break;							\
240 	default:							\
241 		BUILD_BUG();						\
242 	}								\
243 	uaccess_disable_not_uao();					\
244 	(x) = (__force __typeof__(*(ptr)))__gu_val;			\
245 } while (0)
246 
247 #define __get_user(x, ptr)						\
248 ({									\
249 	int __gu_err = 0;						\
250 	__get_user_err((x), (ptr), __gu_err);				\
251 	__gu_err;							\
252 })
253 
254 #define __get_user_error(x, ptr, err)					\
255 ({									\
256 	__get_user_err((x), (ptr), (err));				\
257 	(void)0;							\
258 })
259 
260 #define get_user(x, ptr)						\
261 ({									\
262 	__typeof__(*(ptr)) __user *__p = (ptr);				\
263 	might_fault();							\
264 	access_ok(VERIFY_READ, __p, sizeof(*__p)) ?			\
265 		__get_user((x), __p) :					\
266 		((x) = 0, -EFAULT);					\
267 })
268 
269 #define __put_user_asm(instr, alt_instr, reg, x, addr, err, feature)	\
270 	asm volatile(							\
271 	"1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",			\
272 			alt_instr " " reg "1, [%2]\n", feature)		\
273 	"2:\n"								\
274 	"	.section .fixup,\"ax\"\n"				\
275 	"	.align	2\n"						\
276 	"3:	mov	%w0, %3\n"					\
277 	"	b	2b\n"						\
278 	"	.previous\n"						\
279 	_ASM_EXTABLE(1b, 3b)						\
280 	: "+r" (err)							\
281 	: "r" (x), "r" (addr), "i" (-EFAULT))
282 
283 #define __put_user_err(x, ptr, err)					\
284 do {									\
285 	__typeof__(*(ptr)) __pu_val = (x);				\
286 	__chk_user_ptr(ptr);						\
287 	uaccess_enable_not_uao();					\
288 	switch (sizeof(*(ptr))) {					\
289 	case 1:								\
290 		__put_user_asm("strb", "sttrb", "%w", __pu_val, (ptr),	\
291 			       (err), ARM64_HAS_UAO);			\
292 		break;							\
293 	case 2:								\
294 		__put_user_asm("strh", "sttrh", "%w", __pu_val, (ptr),	\
295 			       (err), ARM64_HAS_UAO);			\
296 		break;							\
297 	case 4:								\
298 		__put_user_asm("str", "sttr", "%w", __pu_val, (ptr),	\
299 			       (err), ARM64_HAS_UAO);			\
300 		break;							\
301 	case 8:								\
302 		__put_user_asm("str", "sttr", "%x", __pu_val, (ptr),	\
303 			       (err), ARM64_HAS_UAO);			\
304 		break;							\
305 	default:							\
306 		BUILD_BUG();						\
307 	}								\
308 	uaccess_disable_not_uao();					\
309 } while (0)
310 
311 #define __put_user(x, ptr)						\
312 ({									\
313 	int __pu_err = 0;						\
314 	__put_user_err((x), (ptr), __pu_err);				\
315 	__pu_err;							\
316 })
317 
318 #define __put_user_error(x, ptr, err)					\
319 ({									\
320 	__put_user_err((x), (ptr), (err));				\
321 	(void)0;							\
322 })
323 
324 #define put_user(x, ptr)						\
325 ({									\
326 	__typeof__(*(ptr)) __user *__p = (ptr);				\
327 	might_fault();							\
328 	access_ok(VERIFY_WRITE, __p, sizeof(*__p)) ?			\
329 		__put_user((x), __p) :					\
330 		-EFAULT;						\
331 })
332 
333 extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
334 #define raw_copy_from_user __arch_copy_from_user
335 extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n);
336 #define raw_copy_to_user __arch_copy_to_user
337 extern unsigned long __must_check raw_copy_in_user(void __user *to, const void __user *from, unsigned long n);
338 extern unsigned long __must_check __clear_user(void __user *addr, unsigned long n);
339 #define INLINE_COPY_TO_USER
340 #define INLINE_COPY_FROM_USER
341 
342 static inline unsigned long __must_check clear_user(void __user *to, unsigned long n)
343 {
344 	if (access_ok(VERIFY_WRITE, to, n))
345 		n = __clear_user(to, n);
346 	return n;
347 }
348 
349 extern long strncpy_from_user(char *dest, const char __user *src, long count);
350 
351 extern __must_check long strnlen_user(const char __user *str, long n);
352 
353 #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
354 struct page;
355 void memcpy_page_flushcache(char *to, struct page *page, size_t offset, size_t len);
356 extern unsigned long __must_check __copy_user_flushcache(void *to, const void __user *from, unsigned long n);
357 
358 static inline int __copy_from_user_flushcache(void *dst, const void __user *src, unsigned size)
359 {
360 	kasan_check_write(dst, size);
361 	return __copy_user_flushcache(dst, src, size);
362 }
363 #endif
364 
365 #endif /* __ASM_UACCESS_H */
366